Elo Terrorist is a term used to describe a player in ranked that intentionally throws one way or another to get their team to lose. This can be through AFK'ing, playing intentionally bad, etc. The term isn't specific to any game but sees most of its use in overwatch 2 and league of legends. What sets this term apart from other terms such as thrower is the consistency, while someone might throw a game when they tilt or get mad at a teammate from time to time, it is usually isolated or from time to time. Elo Terrorists usually stick to one of two methods of elo terrorism, either throwing most of, if not all their games, or exclusively griefing a specific player or players to stream snipe, target a player they don't like from previous game, etc.
These players are either very dedicated trolls or sadistic monsters who thrive off of pulling teammates down with them.
Pigboy: Going 0-12 only in super's games
supertf: Guys I think Pigboy is an elo terrorist.
Cortex is an ecological terrorist because he mutates marsupials and contaminates the gene pool